/* Long Multiplication Calculator - styles v2.0 */

:root {
    /* Palette: WCAG AA contrast on both light and dark schemes. */
    --color-bg: #ffffff;
    --color-text: #1a1a1a;
    --color-muted: #5a5a5a;
    --color-primary: #2b5fb3;
    --color-primary-hover: #1f4485;
    --color-primary-text: #ffffff;
    --color-border: #c0c0c0;
    --color-error-bg: #ffe8d6;
    --color-error-border: #b1452b;
    --color-error-text: #6e2814;
    --color-solution-bg: #fafafa;
    --color-focus: #2563eb;

    --radius: 6px;
    --max-width: 720px;
    --spacing-xs: 4px;
    --spacing-sm: 8px;
    --spacing-md: 16px;
    --spacing-lg: 24px;

    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --font-mono: "Fira Code", "JetBrains Mono", "Source Code Pro", Consolas, "Courier New", monospace;
}

@media (prefers-color-scheme: dark) {
    :root {
        --color-bg: #121212;
        --color-text: #ececec;
        --color-muted: #a0a0a0;
        --color-primary: #6f9bff;
        --color-primary-hover: #9ebbff;
        --color-primary-text: #0c1730;
        --color-border: #3a3a3a;
        --color-error-bg: #3b1d10;
        --color-error-border: #b1452b;
        --color-error-text: #ffd5c2;
        --color-solution-bg: #1c1c1c;
        --color-focus: #9ebbff;
    }
}

* {
    box-sizing: border-box;
}

html, body {
    margin: 0;
    padding: 0;
    background-color: var(--color-bg);
    color: var(--color-text);
    font-family: var(--font-sans);
    line-height: 1.5;
}

main {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: var(--spacing-lg) var(--spacing-md);
}

h1 {
    font-size: 1.6rem;
    margin: 0 0 var(--spacing-md) 0;
}

h2 {
    font-size: 1.2rem;
    margin: 0 0 var(--spacing-sm) 0;
}

a {
    color: var(--color-primary);
    text-decoration: underline;
}

a:focus-visible,
button:focus-visible,
input:focus-visible {
    outline: 2px solid var(--color-focus);
    outline-offset: 2px;
}

.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    margin: -1px;
    padding: 0;
    overflow: hidden;
    clip: rect(0 0 0 0);
    white-space: nowrap;
    border: 0;
}

.divider {
    border: none;
    border-top: 2px dashed var(--color-primary);
    margin: var(--spacing-lg) 0;
    width: 70%;
}

.field {
    margin-bottom: var(--spacing-md);
}

.field label {
    display: block;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.field input {
    width: 100%;
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 1rem;
    font-family: var(--font-mono);
    color: var(--color-text);
    background-color: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
}

.field input:invalid {
    border-color: var(--color-error-border);
}

.hint {
    display: block;
    margin-top: var(--spacing-xs);
    color: var(--color-muted);
    font-size: 0.85rem;
}

.actions {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
    margin-top: var(--spacing-md);
}

button {
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 1rem;
    cursor: pointer;
    border: 1px solid var(--color-primary);
    border-radius: var(--radius);
    background-color: var(--color-primary);
    color: var(--color-primary-text);
    transition: background-color 0.15s ease, color 0.15s ease;
}

button:hover:not(:disabled) {
    background-color: var(--color-primary-hover);
    border-color: var(--color-primary-hover);
}

button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

#clear,
#copy {
    background-color: transparent;
    color: var(--color-primary);
}

#clear:hover:not(:disabled),
#copy:hover:not(:disabled) {
    background-color: var(--color-primary);
    color: var(--color-primary-text);
}

#status {
    margin: var(--spacing-md) 0;
    padding: var(--spacing-md);
    background-color: var(--color-error-bg);
    border: 1px solid var(--color-error-border);
    color: var(--color-error-text);
    font-style: italic;
    border-radius: var(--radius);
}

#status:not([hidden]) {
    display: block;
}

#solution {
    background-color: var(--color-solution-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: var(--spacing-md);
    overflow-x: auto;
    font-family: var(--font-mono);
    font-size: 0.9rem;
    line-height: 1.2;
    white-space: pre;
    margin: 0;
}

#solution .empty-state {
    color: var(--color-muted);
    font-style: italic;
}

footer {
    margin-top: var(--spacing-lg);
    color: var(--color-muted);
    font-size: 0.85rem;
}